递归和回溯_leetcode39

class Solution(object):
    def combinationSum(self, candidates, target):
        """
 :type candidates: List[int]
 :type target: int
 :rtype: List[List[int]]
 """
 self.res = []



 self.generateCombinatio(candidates,target,0,[])

 print self.res

 return self.res


 # start 指示序列的总终止条件
 def generateCombinatio(self,candidates,target,start ,ans):

 if sum(ans) == target:
 self.res.append(ans[0:])
 return

 if sum(ans) > target:
 return

 #[i,n] 防止 重复搜索
 for i in range(start,len(candidates)):

 ans.append(candidates[i])
 self.generateCombinatio(candidates,target,i,ans)
 ans.pop()





s = Solution()
can = [2,3,6,7]
tar = 7

s.combinationSum(can,tar)